"John is a Java expert and was able to help me big time. I had a somewhat technical implementation and John was able to read the documentation and catch on quickly. I've been studying the problem domain for months and he only had three days, but by the middle of it we were talking like peers who had been in the field for years. We also had some technical challenges we overcame and he persisted until the job got done.
He saw I was a student and was very reasonable and didn't charge me for down time where we were downloading things or doing busy work. He didn't have to do that, and not all mentors do, but I appreciated it."